This invention relates to an image forming method and an image forming apparatus applicable to a copying machine or a printer each according to an electrophotographic method.
Recently an organic photoreceptor containing an organic photoconductive substance is widely used in an image forming apparatus according to an electrophotographic method. On the organic photoreceptor, various problems tend to be occurred on cleaning of the toner remained after transferring the toner to the image receiving material since the contact energy of the organic photoreceptor to the toner developing the latent image formed on the organic photoreceptor is large.
An electrophotographic image forming apparatus having a cleaning device just above a cylindrical electrophotographic photoreceptor has been proposed in Japanese Patent Application No. 11-290755. Such the image forming apparatus has an advantage that the apparatus can be made compact. When a blade scrapes the toner at the flank of the cylindrical photoreceptor, the toner is freely falls by the gravitation. However, when the cleaning blade is contacted just above to the photoreceptor, incompleteness of cleaning is often occurred since the toner scraped off by the cleaning blade tends to be remained on the surface of the photoreceptor.
Recently, a digital image forming method has been become as main stream of the image forming method accompanied with the progress of the digital technology. In the digital image forming method, a small dot image such as a image of 400 dpi is developed. Accordingly a high quality image forming technology is required by which such the small dot image can be reproduced with high fidelity.
One of the most important technologies for raising the image quality relates to the production of the toner. Currently, a toner produced by mixing, kneading, powdering and classifying a binder resin and a pigment has been mainly used for forming the electrophotographic image. However, the toner produced by such the process is insufficient in the particle size distribution and the shape uniformity. It is difficult to form an image with a sufficient quality by the use of such the toner.
A electrophotographic developer or an image forming method using a polymerized toner is proposed as the means for achieving the satisfactory particle size distribution and the uniform shape uniformity. The polymerized toner has the satisfactory particle size distribution and the shape uniformity since the toner is produced by polymerizing monomer uniformly dispersed in an aqueous medium.
A problem is newly raised when such the polymerized toner is used in an image forming apparatus having the organic photoreceptor. Namely, the cleaning tends to be incomplete since the shape of the toner particle is almost sphere and has a high attractive force to the organic photoreceptor surface.
Particularly, when the polymerized toner is applied to the image forming apparatus in which the cleaning device is arranged just above the cylindrical organic photoreceptor, very fine toner particles, by which no visible transferred image is formed, are slipped and passed through the cleaning blade and a charging device such as a charging wire or a charging roller is contaminated by such the very fine toner particles for a long period. As a result of the contamination, unevenness in the halftone image is formed.
The object of the invention is to solve the above-mentioned problem and to provide an image forming method and an image forming apparatus by which incomplete cleaning occurred in the image forming apparatus having a cleaning blade arranged just above the cylindrical organic photoreceptor, hereinafter referred to as a cylindrical photoreceptor, an organic photoreceptor or a photoreceptor, is prevented so that the cleaning property is maintained for a long period and a sufficient electrophotographic image without any image defect can be obtained even when the polymerized toner is used.
As a result of the investigation by the inventors, it is made possible that a good cleaning ability is maintained and a satisfactory electrophotographic image is obtained for a long period by using a toner particles having a specific shape factor and reducing the exposed area of the substrate of the organic photoreceptor even though the image forming apparatus having a cleaning blade arranged just above the cylindrical organic photoreceptor. The object of the invention can be achieved by the followings.
1. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
a number ratio of toner particles having a shape coefficient of 1.2 to 1.6 is at least 65 percent in the toner particles.
2. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
number ratio of toner particles having no corners is 50 percent or more with reference to whole toner particles.
3. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
the toner has M of at least 70 percent, M being sum of m1 and m2 wherein m1 is relative frequency of toner particles, included in the most frequent class, and m2 is relative frequency of toner particles included in the second frequent class in a histogram showing the particle size distribution, which is drawn in such a manner that natural logarithm lnD is used as an abscissa, wherein D (in xcexcm) represents the particle diameter of a toner particle, while being divided into a plurality of classes at intervals of 0.23, and number of particles is used as an ordinate.
4. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
the toner has a number variation coefficient of the number distribution of the toner particle of not more than 27%.
5. A method of forming a toner image of claim 4, wherein the toner has a number variation coefficient of the number distribution of the toner particle of not more than 25%.
6. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
the toner has a number variation coefficient of the shape coefficient of the toner particle of not more than 16%.
7. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
the toner contains toner particles having a shape coefficient of from 1.2 to 1.6 in a ratio of not less than 65% in number and a variation coefficient of the shape coefficient of not more than 16%.
8. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
the toner contains toner particles having a variation coefficient of the shape coefficient of not more than 16% and a variation coefficient of the particle number in the particle size distribution of not more than 27%.
9. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
the toner particles are prepared by association of particles obtained by polymerization of monomers in a water based medium.
10. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
contacting width of the cleaning blade is wider than width of the photosensitive layer of the organic photoreceptor.
11. A method of forming a toner image, comprising:
electrically charging a photoreceptor comprising an organic photosensitive layer provided on a cylindrical substrate;
imagewise exposing the photoreceptor so that a latent image is formed on the photoreceptor;
developing the latent image with toner so that a toner image is formed on the photoreceptor;
transferring the toner image to a recording material from the photoreceptor; and
cleaning residual toner on the photoreceptor by cleaning blade; wherein
the photoreceptor is installed so that the center axis of the cylinder is to be almost horizontal,
front edge of the cleaning blade is pressed against surface of the photoreceptor so that cylindrical center angle xcex2 of the cylindrical photoreceptor is at an angle of within xc2x130xc2x0 with respect to 0xc2x0 of the vertical line passing the center axis of the cylindrical photoreceptor,
ratio of width of the photosensitive layer of the photoreceptor to length of the cylindrical electroconductive substrate is 80/100 to 99/100, and
the photoreceptor comprises a protective layer containing a compound containing a fluorine or silicone atom.